Digital BW, The Print

--- In DigitalBlackandWhiteThePrint@y..., "Austin Franklin" <
darkroom@i...> wrote:
> > > This is a fact. Please.  Bit depth IS a limiting factor of
> > dynamic range in
> > > the way current scanners are designed.
> >
> > Austin, here you are saying one thing, below you say another. Ill point
> > it out later.
> 
> I didn't see you point this out anywhere in your post here...  I just don't
> understand why we're discussing this, it's just a plain fact when
> representing INTEGER DENSITY RATIO VALUES (which is how scanners work), the
> number of bits are the limiting factor of the dynamic range.  If you are
> representing some other "values", then the number of bits may or may not be
> the limiting factor.
> 

Never mind about that, I guess when you said "the way current scanners 
are designed" you were correct.

> > Here it is.
> > In this case (and many less extreme ones) how is bit depth the limiting
> > factor?
> >
> > All scanners used to be only 8bit, but they still captured film with
> > the same d-range that the film we scan today has.
> 
> Show me one example of a scanner that used 8 bits, and captured a dynamic
> range of 3.2 or greater.  They may have RETURNED 8 bits of data, after the
> setpoints and curves were done in the scanner driver...but the actual A/D
> output was much higher.

I don't know about 3.2 drange, but how about the Microtek 300Z or the 
Apple One Scanner.


> > > > Bit
> > > > depth is how many tones are used within the dynamic range,
> > not how many
> > > > tones it takes to give you dynamic range.
> > >
> > > No, that isn't how scanners are designed.  Bit depth does
> > nothing but expand
> > > the tonal capture ability into the dark regions...it does NOT give more
> > > tones within the same dynamic range...for the same image
> > (unless the image
> > > is clipping).
> >
> > It does if you are talking about the old scanners vs the new.
> 
> Show me an "old" scanner that does as you claim.
> 
> > There is
> > no reason to limit ourselves by saying todays scanners give us more
> > than we could ever use. Film is analog, scanner makers should come out
> > with a scanner that captures the full 16bits with a density range of
> > todays 14bit scanners. Which would entail differentiating more tones
> > rather than the ability to capture a more dense negative.
> 
> That is not necessarily true.  Because it's analog, doesn't mean it's
> infinite.  You're forgetting a little thing called noise.  Noise will limit
> the number of tones you can get.
> 
> > I am not
> > saying it is possible, but I would think someone would be able to
> > figure it out.   Nobody has yet because it hasn't been necessary...
> 
> It IS possible, I've already "figured it out", but, as you say, it just
> isn't necessary.  It's actually very simple.  The data out of the A/D does
> not represent integer density ratio values, but fractional density ratio
> values.

Why do they have to be integers?


> > I have taken issue with the term dynamic range. Scanner companies use
> > it to mean their scanners capture more information.
> 
> The term "dynamic range" has been around long before scanners, and has a
> fixed meaning in the engineering community.  Because it is
> misrepresented/misunderstood by some does not change the definition of it.

The dynamic range of sound does not relate to the intensity (volume)

> > If a
> > scanner could really capture 4.5 density-range in a 12 bit space,
> 
> As I've said, you CAN capture (if you design a scanner to do so) any density
> range into 2 or more bits...BUT...the values you get are NOT integer density
> ratio values.

Who says they have to be integers?

> > then
> > a normal negative's range would have to fit into a much smaller space
> > than 12 bits.
> 
> For that particular scanner, IF that scanner was designed to operate that
> way, that could be true.  Perhaps the scanner could expand the data to fit
> the entire 12 bits.
> 

Wouldn't this be something we would want? Does this throw off the look 
of the image in some way (emphasizing certain tones more than others or 
something)? I am just trying to think of why this isn't done other than 
to make a scanners specs look better by saying it can capture something 
ridiculous like 4.5

> > Which would mean that, with that negative, that scanner
> > would actually capture less information than a 3.3 d-range, 12 bit,
> > scanner.  Does this make sense?
> 
> Only if the scanner was designed to operate that way.

I am thinking that this would be true with the scanners on the market 
now, yes?

> 
> > That is one of the reasons I think they should have called it density
> > range. And left the term dynamic range to something more along the
> > lines of bit depth.
> 
> But they are both the exact same thing.  Density is a ratio, just like
> dynamic range is.

Yes and no, density is a ratio compared to the darkest one can see. 
Dynamic range is a ratio compared to the sublest change one can see.
Because of the way scanners are made, they end up being the same.

-mikeH